Scientists have found that those who run barefoot, or in minimal footwear, tend to avoid “heel-striking,” and instead land on the ball of the foot or the middle of the foot. In so doing, these runners use the architecture of the foot and leg and some clever Newtonian physics to avoid hurtful and potentially damaging impacts, equivalent to two to three times body weight, that shod heel-strikers repeatedly experience.

Researchers have actually quantified the nutritional consumption of riders in the Tour de France (1991 Tour), and the Tour of Spain (1998 Tour), and measured that riders average a daily food intake of 4,000 to 8,000 calorie

Daily carbohydrates consumed by a Tour De France rider

It is estimated that the Tour de France requires a carbohydrate intake of 13 g/kg (6 g/lb.) of body weight, and they need to intake these amounts day after day.

Another interesting analysis is from sports scientists.They have a neat anaylsis on how much a 78Kg rider will need to consume to avoid fatigue and remain competitive. Read it at sports scientist